In the original Pokémon Red/Blue, When you encounter your rival in Lavender Town, he asks whether or not you know what it's like to have one of your Pokémon die. At this point in the game, he no longer has his Raticate that he used in previous battles.

Your Rival battle before this took place aboard the S.S. Anne. Your rival's Raticate sustained serious injuries from the battle but, because of crowding and confusion on the luxury liner, he was unable to make it to the Pokémon Center in time and the Raticate passed away. The real reason your rival is in Lavender Town to begin with is to lay his deceased friend to rest.

Despite all of this, your rival never outwardly tells you that you're responsible for the death of his Pokémon. He hides his grief and instead channels that energy into the motivation he needs to continue his quest to become Indigo League Champion. The death of his Raticate effectively destroys your rival's impish, childhood innocence. Although he tells himself that he doesn't hold you responsible, he subconsciously holds a great deal of resentment towards you which further fuels his ambitions.

Tearfully swearing upon his Raticate's grave not to fail in what he set out to do, he trains hard in hopes of becoming better than you... Defeating you... and to eventually make it to the Pokémon League.

Mere moments after he became Indigo League Champion, he was defeated... be you. Although he fulfilled his promise to his Pokémon, it was only for a painfully brief instant.

In the end, your rival is scolded by his grandfather while you receive the professor's praise. During the course of the game, you steal your rival's innocence, crush his dreams, and ultimately snatch away the love of his grandfather.

back in my day we didn't have any fancy Pokeman. we had to gather insect and have them fight for real, i used a praying mantis and it beat every other bug out there, till one day the school bully smashed it, we got in a fist fight and later our parents had us apologies to each other. We got in a fight half way through our "apologies" then we got grounded with no supper. later at school he said he was sorry, and I forgave him. then we fought for the hell of it. and that is how school yard fight club got started. we met back up in the army years later, we spared with each other for the hell of it and became good friends, till that jackass left me alone in the fox hole... turned out he got taken to a P.O.W camp. never did see him again. but I heard he was being given a Medal of Honer. I got one to but a year earlier. cause I wasn't a P.O.W.